1. Field of the Invention
The present invention relates to wood based panels having a wood like texture suitable for use as ceiling, wall panels and the like, and to their method of manufacture.
2. Background Art
Desirable properties for panel materials used for ceilings, walls and the like are light weight, sound absorbent, incombustible or semi-incombustible, and have good thermal insulating ability, high rigidity, good workability, and a wood like texture.
Up until now, a variety of materials have been sold for use as ceiling and wall linings.
For example, various types of these materials include:
(a) panels consisting mainly of rock wool;
(b) panels made from phenol, aluminum hydroxide, glass fiber and the like;
(c) calcium silicate panels, plaster board panels etc.; and
(d) panels consisting mainly of wood such as standard wood board, plywood, particle board, and fiber board.
However, of the types of conventional panel materials mentioned above, the type (a) panels consisting mainly of rock wool, although being inflammable and sound absorbent, have a specific gravity greater than 0.4, do not have a wood like texture, are easily broken when bent, and have poor rigidity and workability. The type (b) panels made from phenol, aluminum hydroxide, glass fiber and the like have a high specific gravity of approximately 0.45, poor sound absorption properties, and high cost. The type (c) calcium silicate boards and plaster boards have a high specific gravity of around 0.7, and reflect sound with minimal sound absorption. The type (d) panels which consist mainly of wood such as standard wood board, plywood, particle board, fiber board and the like utilize wood and hence are rigid and exhibit a wooden texture. However they are combustible, limited in use due to interior finishing restrictions, and the specific gravity is high.
Furthermore, when wood based panels are formed with the wood fibers packed tightly together, thermal conductivity is increased, and acoustic absorptivity drops with a reduction in thermal insulating and sound absorption properties, and the wood like texture of the panel surface is lost.
To obtain good sound absorption and thermal insulating properties, with a wood like textured surface, it is necessary to form the panel with the wood fibers less tightly packed together, at a lower density, so that air voids are suitably dispersed throughout.
Up until now, the production of such wood like panels has involved a wet type method wherein disk-fiberized wood fibers are dispersed in a large amount of water, additives such as binders are then added and the mixture stirred. The material is then spread out in the manner of making paper and hot pressed.
With this method, however, heating and pressing the material in the moist condition results in the wet softened wood fibers being compressed and tightly packed together. At the same time, a physical and chemical change occurs in the constituent elements of the wood fiber, so that the bonding between the fibers is remarkably increased.
Accordingly, with panels formed by the wet method, since the wood fibers are tightly and securely packed together, the panel has high acoustic and thermal conductivity, so that sound absorption and thermal insulating properties are reduced, and a wood like texture is not possible.